Ocean Liberator
And of course the most important reason is cost. Cutting steel with plasma produces highly carcinogenic dust that MUST be captured in a dust extraction filtering system. This as well as the cost to completely enclose the machine to evacuate the dust raises the price to far beyond what our typical fabricator is prepared to pay for a beam coping solution.
Another drawback is that when cutting thicker areas of a part, even on light wide-flange beams, for instance the radius at the intersection of the web and the flange, it is typical for the flame to blow back, and this can and cause damage to the plasma head.